Luna 24

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Luna 24 was the third attempt to recover a sample from the unexplored Mare Crisium, the location of a large lunar mascon (after Luna 23 and a launch failure in October 1975). After a trajectory correction on 11 August 1976, Luna 24 entered lunar orbit three days later. Initial orbital parameters were 115 by 115 kilometres (71 by 71 mi) at 120° inclination. After further changes to its orbit, Luna 24 set down safely on the lunar surface at 06:36 UT on 18 August 1976 at 12°45' north latitude and 62°12' east longitude, not far from where Luna 23 had landed.[1] Exact landing location (12.7145° N, 62.2097° E) was determined by the Lunar Reconnaissance Orbiter probe orbital cameras in 2012.[2]

Under command from ground control, the lander deployed its sample arm and pushed its drilling head about 2 metres into the nearby soil. The sample was safely stowed in the small return capsule, and after nearly a day on the Moon, Luna 24 lifted off successfully at 05:25 UT on 19 August 1976. After an uneventful return trip, Luna 24's capsule entered Earth's atmosphere and parachuted safely to land at 17:55 UT on 22 August 1976, about 200 kilometres (120 mi) southeast of Surgut in western Siberia. Study of the recovered 170.1 grams (6.00 oz) of soil indicated a laminated type structure, as if laid down in successive deposits. The Soviet Union swapped a gram of the mission sample for a lunar sample from NASA in December 1976.[1] Luna 24 was the last lunar spacecraft to be launched by the Soviet Union. It was also the last spacecraft to make a soft landing on the Moon until the landing of Chang'e 3 on December 14, 2013, 37 years later.

In February 1978 soviet scientists M. Akhmanova, B. Dement'ev, and M. Markov of the Vernadsky Institute of Geochemistry and Analytic Chemistry published a paper claiming a detection of water fairly definitively.[3][4] Their study showed that the samples returned to Earth by the probe contained about 0.1% water by mass, as seen in infrared absorption spectroscopy (at about 3 µm wavelength), at a detection level about 10 times above the threshold.[5]